1. Field of the Invention
The present invention relates to saw chain cutting elements such as cutting links and in particular it relates to a cutting element and structure therefore for sawing hard, abrasive aggregate material.
2. Background of the Invention
Chain saws are efficient tools for cutting hard, abrasive material including aggregate materials such as formations of rock and stone, composite mixtures such as concrete, building blocks, brick and the like. Chain saws adapted for use on such aggregate materials take the general form of traditional chain saws as applied to wood products. The cutting elements of a saw chain for cutting hard abrasive material differ widely, however, from the traditional wood cutting saw chain.
The saw chains for cutting hard abrasive materials generally utilize rectangular cutting blocks mounted to support links of the saw chain. The cutting blocks are typically a matrix of material in which hard wear resistant cutting elements such as industrial diamonds are randomly distributed. The cutting blocks vary in several respects but generally are fixedly attached across a side link pair of the saw chain such as by weldments. Regardless of their configuration, they present a large surface area of the cutting block for abrading contact with the material to be cut, and the blocks are arranged so that the saw kerf produced exceeds the width of the basic chain chassis.
Cutting aggregate material is an abrading or crushing action rather than a severing, i.e., chip removal, action. The cutting blocks establish surface-to-surface contact with the material to be cut and the movement of blocks and pressure against the material reduces the material to fine particles. The aggregate material and the fine particles produced are very abrasive. The abrasive nature of this material inflicts severe wear conditions upon the saw chain components. The saw chain traveling in the kerf rubs against the side walls of the kerf, and this can rapidly wear away the saw chain rivet heads. A further problem is that the leading edge of the block produces the greatest cutting action and experiences the greatest wear. The area of the block succeeding the leading edge tends to inefficiently re-crush the material already removed, rather than productively remove additional material. The result is an inefficient use of the succeeding portions of the block.
Another problem with such cutting blocks, has been the uneven distribution of the cutting elements throughout the matrix. As the cutting block wears down, the number of exposed cutting elements, e.g., diamonds, can vary, i.e., more or fewer diamonds being exposed along one cutting area than another. Also, the leading and side edges of the block tend to erode or wear away at a faster rate than the rest of the block resulting in a crowned wear pattern. This crown makes it difficult to maintain the kerf width. As the blocks become tapered due to the crowned wear pattern, the chain can bind in the kerf. Kerf width is better maintained by removing the material in the corners of the kerf, but the corners of the cutting blocks tend to be the weakest part of the cutting block and often fail in this respect. Also, the corners of the kerf are not under the same constant cutting action as is the center portion of the kerf. This is due in part to assembly tolerance, i.e., lateral misalignment of individual blocks on the chain. A first block may be well centered on the chain and produce the desired kerf, but a succeeding block may be laterally offset. The outward extending corner of the offset block removes additional material, i.e., outside the desired kerf width, while the opposite corner does little or no cutting. Other blocks must remove the material skipped in the kerf corner by the offset block. Overall, the cutting block corners experience greater wear.
Accordingly, it is desirable that a saw chain for cutting aggregate material be better adapted to withstand the abrasion present in such cutting environments but with more efficient use of the abrasive particles, and better maintain a desired kerf width for improved cutting with less operator applied force. The subject matter of the present invention provides these and other advantages for an aggregate cutting saw chain.
Abrasive tools have heretofore included a diamond mesh cutting element whereby an underlying mesh structure receives a well distributed collection of hard particles, e.g., industrial diamonds, and the entire assembly is secured as a composite material by compression and sintering. Such composite material abrasive tools are shown and described in U.S. Pat. No. 5,049,165 issued Sep. 17, 1991 to Naum N. Tselesin, and entitled Composite Material; and in U.S. Pat. No. 4,925,457 issued May 15, 1990 to Peter T. deKok and Naum N. Tselesin and entitled Abrasive Tool and Method for Making. The disclosures of U.S. Pat. Nos. 4,925,457 and 5,049,165 are herewith incorporated fully herein by reference.